IOLs are commonly implanted in the eye to treat certain conditions, such as cataracts or myopia. For example, an IOL is implanted in the eye as a replacement for the natural crystalline lens after cataract surgery or to alter the optical properties of an eye, such as by providing vision correction, in which the natural lens remains. The IOL provides the light focusing function originally undertaken by the crystalline lens. Insertion of an IOL for the treatment of cataracts is the most commonly performed eye surgical procedure. Each year approximately 1.4 million people in the United States alone undergo cataract surgery.
A typical IOL includes an optic or lens body for focusing light toward the retina of the eye. In addition, the IOL also includes one or more fixation members or haptics for securing the IOL in the desired position within the chamber of the eye. The IOL is implanted directly into the eye through a small incision formed in the ocular tissue of the eye. To fit through this small incision, modern IOLs, which are made from soft, biocompatible materials, are designed to be deformed, e.g., rolled, folded or the like, to a relatively small profile before being injected into the eye and then allowed to return to their original shape within the eye.
Generally, IOL insertion devices use a plunger to insert the IOL into the eye. It is advantageous to have a small incision in the eye to insert an IOL. Accordingly, a small diameter tube that tapers is typically used. As the IOL progresses down the tapering tube, increased force is needed. Then, as the IOL is being expelled, the resistant force dramatically decreases. Consequently, the expelled IOL has a tendency to pop open into place within the eye. Thus, in existing plunger-type IOL insertion devices, there is an increased risk of damaging the eye if the IOL rapidly expels out of the insertion device. This phenomenon of an IOL rapidly ejecting due to a decrease in resistant force is commonly referred to as popping.
Therefore, it would be highly beneficial to provide an IOL insertion device that facilitates the injection of the IOL in a controlled manner by dampening the acceleration that occurs as the IOL is pushed out of the insertion device. Furthermore, it would be beneficial for the insertion device to provide an adaptive or accommodative force that changes depending upon the amount of force imparted on the plunger by the user.